Astronomers have found that the atmosphere of the hottest known exoplanet, the hot Jupiter-like planet KELT-9b, is "boiling off," with the escaping gas being captured by the host star. Using the CARMENES instrument at Calar Alto Observatory, Fei Yan and Thomas Henning of the Max Planck Institute for Astronomy in Heidelberg were able to detect the escaping hydrogen atmosphere of the planet. Their observations indicate a spread-out hydrogen envelope that is being pulled towards the host star.